This invention relates to a photosensitive polymer composition which can form a polyimide of excellent heat resistance.
Thermosetting type polyimides have hitherto been used as interlayer insulating films or surface-protecting films for semiconductor elements, LSIs, etc. (U.S. Pat. No. 3,179,614, U.S. Pat. No. 3,179,634). It is because the thermosetting type polyimides have such characteristics as (i) they can be made into a film easily, (ii) they can be flattened easily and (iii) they have excellent heat resistance.
In recent years, there has been a request for further shortening and rationalization of the step of forming the above films of the thermosetting type polyimides without sacrifying their characteristics (i) to (iii).
In response to the request, there have been proposed photosensitive polymer compositions endowed with photosensitivity and using a poly(amic acid). Specifically, the following photosensitive polymer compositions (1) and (2) have been known.
(1) A photosensitive polymer composition comprising a poly(amic acid), an amine compound having a group having a hydrogen atom combined with a tertiary or secondary carbon or an unsaturated bond-containing amine compound, and a bisazide. (Japanese Patent Appln. Kokai (Laid-Open No. 168942/82).
(2) A photosensitive polymer composition comprising a poly(amic acid) and an amine compound having, in the molecule, an aromatic bisazido group or a sulfonylazido group (Japanese Patent Appln. Kokai (Laid-Open) No. 102926/82).
In actual formation of an interlayer insulating film or a surface protecting film for semiconductor elements, LSIs, etc. by the use of the above photosensitive polymer compositions (1) and (2), there is employed a process in which a varnish containing such a photosensitive polymer composition is coated and dried, a light is irradiated thereon through a photomask, a wet development is conducted and, lastly, the remaining solvent, amine and azide are evaporated.
However, in the pattern formation according to the above process by the use of the photosensitive polymer composition (1) or (2), there frequently occurred, at the time of development, cracking followed by pattern cutting. Although the cause has not yet been made clear, the tendency was more striking when the time of leaving the film to stand from drying to development was longer.